The present invention relates to liquid crystal devices having flexible substrates.
The plastic substrate LCD technology provides substantial advantages of manufacturing cost, durability, and thinness. However, one respect in which the known plastic LCD technology could be improved is avoidance of separation of substrates at the corners. That is, the prior art plastic LCD device usually has the substrate portions protruding slightly beyond the glue seal, as shown in FIG. 1, so that the corner of the glue perimeter seal is a very high stress point, where the two substrates could conceivably be pried apart.
Thus, it is an object of the present invention to provide a method for sealing the perimeter of a liquid crystal device, so that points of maximum stress are reinforced to prevent separation of the substrates.
A further complication in assembly of flexible substrate liquid crystal devices is that the inner surface of the substrate is typically not particularly good for adhesion. That is, deposition of the alignment layer and metallization layers are likely to degrade adhesion of the perimeter areas in which adhesion must be attained, even if those perimeter areas are screened off or attempted to be screened off during deposition of the alignment and metallization layers.
Thus a further object of the present invention is to provide a method for sealing displays made with flexible substrates together, using a sealing means which is not solely dependent on adhesion to the inner surface of the substrate.
The present invention teaches formation of holes in the upper and lower substrates, at the substrate perimeter area. Thus, not only does the perimeter seal glue establish surface-to-surface cohesion over the relatively limited area of the perimeter seal, but also, at the reinforcement holes, glue adheres to the sidewalls of the holes in the upper and lower substrates, so that what is in effect a rivet of hardened glue secures the substrate adhesion at the maximum stress points.
According to the present invention there is provided: a method for assembling a liquid crystal device, comprising the steps of: providing first and second flexible substrates, each said substrate being provided with a conductor layer, and an alignment layer over said conductor layer, on a first surface thereof; providing reinforcement holes near the perimeter of at least one said substrate; providing glue around the perimeter of said first face of at least one of said substrates; and gluing said first and second substrates together, so that said glue forms a perimeter seal to define an enclosed cavity between said first substrate and said second substrate, and introducing glue into said reinforcement holes.
According to the present invention there is also provided: a liquid crystal device, comprising: a first substrate comprising a flexible material, said first substrate having a conductor layer, and an alignment layer on said conductor layer, on at least a central portion of a first surface of said substrate; a second substrate, comprising a flexible material, said first substrate having a conductor layer, and an alignment layer on said conductor layer, on at least a central portion of a first surface of said substrate; said first and second substrates being joined along the respective perimeters thereof by a glue seal, said glue seal extending along substantially the entire perimeter of said first and second substrates, said first and second substrates being joined so that said first surfaces of both said substrates mutually face together and define a cavity therebetween; a liquid crystal material filling said cavity; at least one said substrate containing reinforcement holes near the perimeter of said first face thereof, said holes being at least partially filled with hardened glue.